Bud rot (BR), caused by Phytophthora palmivora, is one of the most devastating diseases affecting oil palm. It has destroyed oil palm plantations in countries throughout Latin America. To assess their resistance to BR, two cultivars of African oil palm (Elaeis guineensis Jacq.) and two interspecific OxG (E. oleifera × E. guineensis Coari × La Mé and Coari × Pobè) hybrids were planted under field conditions in a plantation with a strong presence of BR. Incidence and severity data were recorded for 1812 days from the date of planting; the disease index was estimated, and progress curves were constructed and adjusted to monomolecular, logistic and Gompertz models. Severity progression and incidence progression rates for each cultivar were estimated using a simple linear regression. Statistical comparisons of the parameters were performed using Student's t-tests. Survival analyses were performed for each of the cultivars. Log-rank statistics were used to compare the responses of the cultivars to BR. Severity progression in the interspecific hybrids was significantly slower than that in the E. guineensis cultivars. No statistically significant differences were found in the progression rates among the hybrids; however, the survival analysis did show statistically significant differences. The Coari × Pobè hybrid had the longest survival time. Considering that partial resistance does not prevent plants from becoming infected but does slow disease progression, the two evaluated hybrids may have commercially valuable levels of resistance.

Palms planted in an area with a high bud rot disease (BR) inoculum pressure were evaluated monthly for a six-year period to determine their tolerance, resistance, or susceptibility to the disease. Dura-type E. guineensis and OxG (E. oleifera × E. guineensis) interspecific hybrids Coari × La Me were evaluated. Of the two types of genetic material evaluated, the progenies of the E. guineensis palms showed the highest levels of incidence, reaching 90% affected palms in less than two years of evaluation. Although the hybrids showed susceptibility, they had a lower degree of affectation than the dura-type palms. The severity assessment of both genetic materials showed that the dura-type palms had the highest degree of affectation, reaching the highest values after over two years of evaluation. However, the hybrids, which were not homogeneous in terms of the level of severity, did not exceed, on average, severity level 2. According to the scale, severity level 2 is indicative of tolerance to the disease.